In general, the invention relates to controlled vehicle suspension systems. More specifically, the invention relates to coefficients of force being offset through suspension damping, and in particular, to a method and system for providing individual wheel control independent of vehicle body forces, for use with suspension damping control outputs.
Known variable force suspension systems include variable force shock absorbers and/or struts that provide suspension-damping forces at a magnitude controllable in response to commands provided by a suspension system controller. Some systems provide control between two damping states and others provide continuously variable control of damping force.
In a known manner of control of a variable force suspension, the demand force for each variable force damper is determined responsive to a set of gains, the wheel vertical velocity and the body heave, roll and pitch velocities. An example system determines the demand force as follows: DF=GhHxe2x80x2+GrRxe2x80x2+GpPxe2x80x2+Gwv, where DF is the demand force, Gh is the heave gain, Gr is the roll gain, Gp is the pitch gain, Gw is the wheel velocity gain, Hxe2x80x2 is the body heave velocity, Rxe2x80x2 is the body roll velocity, Pxe2x80x2 is the body pitch velocity and v is the wheel vertical velocity. The portion of the demand force computation GhHxe2x80x2+GrRxe2x80x2+GpPxe2x80x2, represents the body component determined responsive to the body heave, roll, and pitch velocities. The portion of the demand force computation Gwv represents the wheel component determined responsive to the difference between the computed body corner velocity and the body-wheel relative velocity.
A control signal representing the determined demand force is output to control the variable force damper responsive to the demand force. Example variable force damper systems are described in U.S. Pat. Nos. 5,235,529; 5,096,219; 5,071,157; 5,062,657 and 5,062,658. As previously mentioned, current variable force damper systems require both body and wheel input variables to compute the wheel component demand force. Due to the necessity to use both body and wheel input variables, it is difficult for current variable force damper systems to obtain acceptable levels of wheel control without creating undesirable effects on other aspects of a vehicles ride comfort.
Modules are typically used by the variable force damper systems for identifying and controlling the different aspects of automotive control including the body and wheel components. The modules typically use specialized algorithms designed for interpreting the automobiles input forces for a preferred control signal. One module known in the art commands individual damper outputs to a minimum damping state whenever the applicable desired force and damper wheel to body velocity signals are opposite in sign (a state in which the given damper is said to be in an xe2x80x9cactivexe2x80x9d quadrant). Within the limits of damper travel for small to medium-sized inputs, this approach provides acceptable vehicle body motion control. However, this strategy is insufficient by itself to provide acceptable levels of wheel resonance control.
Therefore, it would be desirable to have a method and system that would improve upon the above-mentioned situation, and related situations in which variable force damper control is reliant on both body and wheel input variables. Such an algorithm may provide superior gross motion control and reduced wheel hop. Ideally, the algorithm would improve body and wheel control with minimal if any sacrifice in the vehicles ride comfort and safety.
One aspect of the invention provides a method for controlling a variable force damper system, including receiving at least one relative velocity signal. At least one body demand force is received. At least one body damper command based on the body demand force is received. At least one wheel motion indicating parameter based on the relative velocity signal is determined. At least one wheel damper command based on the wheel motion indicating parameter is determined and a damper command based on the larger of the body damper command and the wheel damper command is determined.
Other aspects of the invention provide a method where the wheel frequency isolation filter includes a digital band-pass filter. The digital band-pass filter can include a low-pass filter, and a high-pass filter. A slew rate limited can be applied to the wheel damper command. The wheel damper command can be determined by a lookup-table function. The lookup-table function can be based on a linear interpolation function. The lookup-table function can be based on a standard interpolation function. The lookup-table function can be a based on an inherent interpolation function.
Another aspect of the invention provides a method for controlling a variable force damper system, including determining an active quadrant flag based on a supplied body demand force and a supplied relative velocity signal wherein the active quadrant flag may be active or passive. A first body damper command can be determined based on the supplied body demand force. A second body damper command can be determined based on the active quadrant flag wherein the second body damper command is equal to zero when the active quadrant flag is active. The second body damper command can be determined based on the active quadrant flag wherein the second body damper command is equal to the first body damper command when the active quadrant flag is passive. A second wheel damper command can be determined based on the active quadrant flag wherein the second wheel damper command is equal to a function of a supplied wheel damper command and the first body damper command when the active quadrant flag is active and the second wheel damper command can be determined based on the active quadrant flag wherein the second wheel damper command is equal to the supplied wheel damper command when the active quadrant flag is passive.
Other aspects of the present invention provide a method where the determining of the second wheel damper command further includes subtracting the first body damper command multiplied by a pre-defined scaler from the supplied wheel damper command when the active quadrant flag is active and setting the second wheel damper command to equal zero when the second wheel damper command is less than zero.
Another aspect of the present invention provides a method for controlling a variable force damper system, including receiving at least one relative velocity signal. At least one body demand force is received. A body demand force power signal is determined as the product of the body demand force and the relative velocity signal. A body control active quadrant flag responsive to the body demand force power signal is determined wherein the body control active quadrant flag may be active or passive. A body damper command is determined responsive to the body demand force when the body control active quadrant flag is passive, and zero otherwise.
Other aspects of the present invention provide a method in which the body control active quadrant flag is set to active when the body demand force signal is less than a first pre-defined value and set to passive when the body demand force power signal is greater than a second pre-defined value.
Another aspect of the present invention provides a system for controlling a variable force damper system, including a means for receiving at least one relative velocity signal, means for receiving at least one body demand force, means for determining at least one body damper command based on the body demand force, means for determining at least one wheel motion indicating parameter based on the relative velocity signal, means for determining at least one wheel damper command based on the wheel motion indicating parameter; and means for determining a damper command based on the larger of the body damper command and the wheel damper command.
Another aspect of the present invention provides a day system for controlling a variable force damper system, including means for determining an active quadrant flag based on a supplied body demand force and a supplied relative velocity signal wherein the active quadrant flag may be active or passive, means for determining a first body damper command based on the supplied body demand force, means for determining a second body damper command based on the active quadrant flag wherein the second body damper command is equal to zero when the active quadrant flag is active, means for determining the second body damper command based on the active quadrant flag wherein the second body damper command is equal to the supplied body damper command when the active quadrant flag is passive, means for determining a second wheel damper command based on the active quadrant flag wherein the second wheel damper command is equal to a function of a supplied wheel damper command and the first body damper command when the active quadrant flag is active, and means for determining the second wheel damper command based on the active quadrant flag wherein the second wheel damper command is equal to the supplied wheel damper command when the active quadrant flag is passive.
Other aspects of the present invention include a system wherein the means for determining the second wheel damper command further includes means for subtracting the first body damper command multiplied by a pre-defined scaler from the first wheel damper command when the active quadrant flag is active, and means for setting the second wheel damper command to equal zero when the second wheel damper command is less than zero.
Another aspect of the present invention provides a system for controlling a variable force damper system, including means for receiving at least one relative velocity signal, means for receiving at least one body demand force, means for determining a body demand force power signal as the product of the body demand force and the relative velocity signal, means for determining a body control active quadrant flag responsive to the body demand force power signal wherein the body control active quadrant flag may be active or passive, means for determining a body damper command responsive to the body demand force when the body control active quadrant flag is not set, and zero otherwise.
Another aspect of the present invention provides a computer readable medium storing a computer program including computer readable code for receiving at least one relative velocity signal, computer readable code for receiving at least one body demand force, computer readable code for determining at least one body damper command based on the body demand force, computer readable code for determining at least one wheel motion indicating parameter based on the relative velocity signal, computer readable code for determining at least one wheel damper command based on the wheel motion indicating parameter, and computer readable code for determining a damper command based on the larger of the body damper command and the wheel damper command.
Another aspect of the present invention provides a computer readable medium storing a computer program includes computer readable code for determining an active quadrant flag based on a supplied body demand force and a supplied relative velocity signal wherein the active quadrant flag may be active or passive, computer readable code for determining a first body damper command based on the supplied body demand force, computer readable code for determining a second body damper command based on the active quadrant flag wherein the second body damper command is equal to zero when the active quadrant flag is active computer readable code for determining the second body damper command based on the active quadrant flag wherein the second body damper command is equal to the first body damper command when the active quadrant flag is passive, computer readable code for determining a second wheel damper command based on the active quadrant flag wherein the second wheel damper command is equal to a function of a supplied wheel damper command and the first body damper command when the active quadrant flag is active, and computer readable code for determining the second wheel damper command based on the active quadrant flag wherein the second wheel damper command is equal to the supplied wheel damper command when the active quadrant flag is passive.
Other aspects of the present invention include computer readable medium where the computer readable code for determining the second wheel damper command further includes computer readable code for subtracting the first body damper command multiplied by a pre-defined scaler from the supplied wheel damper command when the active quadrant flag is active and computer readable code for setting the second wheel damper command to equal zero when the supplied wheel damper command is less than zero.
Another aspect of the present invention includes computer readable medium storing a computer program including computer readable code for receiving at least one relative velocity signal, computer readable code for receiving at least one body demand force, computer readable code for determining a body demand force power signal as the product of the body demand force and the relative velocity signal, computer readable code for determining a body control active quadrant flag responsive to the body demand force power signal, computer readable code for determining a body damper command responsive to the body demand force when the body control active quadrant flag is passive, and zero otherwise.
The foregoing and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiment, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.